Are the above configuration sufficient for my needs??
I spoke with dell's technical team & they said that if I buy a graphic card & and use it with the DELL system then it will violate the warranty. Can't the dell systems be upgraded.

May I ask why you are looking toward a dell?? Reason I am asking is cause you can get a superior machine for around the same price on other websites.
That graphics card should be more than enough to run those type's of games.

That system should be fine, but for gaming the Intel core i5 2500k or i7 2600k will blow a phenom x6 out of the water. Games rarely make use of more than two cores and I am not aware of any that make use of more than 4 at the moment.

The big question is how much are you paying for this. If you are up to building your own system you can probably do it for much cheaper than dell. If you need a pre-built system there are other companies that build custom computers often for better prices than dell offers, particularly for high end systems.
(And before anyone looks in my detailed profile under system #2 and calls me a hypocrite, Yes my server is a Dell but I bought it off-lease for much cheaper than what I could have built an equivalent system for.)

Again check the power supply. Most newer dell systems I've seen use Delta power supplies, delta is a major OEM with a very good reputation so if it's a delta with decent wattage you should be fine. I have however seen a few dell systems with Bestec power supplies which have a much poorer reputation and should be avoided.

As for the warranty, that is standard with pre-built/ factory made computers. You can physically upgrade it but any upgrade parts not purchased through the manufacture (dell does sell upgrades on their web site at a healthy markup) will void your warranty.

He has already said he can't assemble a PC and his issue may be where he lives as to what options are open to him. Though being able to build your own or having someone else build is without-a-doubt the best way to go.

Games are more GPU intensive than CPU intensive plus the cost of an i7 2600 may be prohibitive. I have a friend whose gaming PC runs a 1055 Thuban and it doesn't miss a beat and he is running some high intensive games on a 27" monitor. He throws the latest and greatest at it and it doesn't even stress it.

I just checked on the power supply used in that system. It is a 460w Delta. This Power supply is of decent quality and is sufficient for the factory configuration, however at 460w it doesn't leave much room for future upgrades.

Route 44 does have a valid point the phenom is cheaper and should be more than sufficient, but again it depends on what you are paying

I ran that config on Dell's website and it came to $990 without the monitor. For that price you could easily get an i5 2500k (posibly a i7 2600k) from someone like cyberpower PC, iBuyPower or other custom manufactures. For the most part pre-built systems with the phenom X6 seem to be around the same price as the i5 2500k even though the X6 1090 is about $50 cheaper than the 2500k.

Again it depends what the system is being used for. For gaming the i5 2500k would be a better option, for heavily multithreaded business applications or serious multi-tasking the X6 may be a better bet since then you may take advantage of the additional cores.

Also just for reference I ran a similar configuration to the dell through Newegg (with a better PSU) and it comes to around $600 in parts (all high quality name brands) + $140 for a windows liscense, so if you have any local computer shops check with them, they may be able to build a system with those specs for less than a national manufacture.

Where the GTX560 Ti has it over the ATI 6770 is a 256-bit interface as opposed to a 128-bit interface.

Second, I agree with dmil89 on the i5 2500k as a good bet here. Many people choose it over the i5 2600k because there isn't that big of a performance difference at stock and it is cheaper. Also, pay attention to what he said about power supplies and future upgrading because your system should be good for at least three years and will probably only need a power supply and video card upgrade at that when the time comes.

Again, the issue for gaming is the graphics card and all three cpus we have discussed will more than meet your gaming needs. I would say if they offered your original choice with either the ATI 6850 or 6950 making the choice would be even more difficult.

Dell isn't going to build you a system with incompatible hardware so you should be fine without needing to worry about compatibility. If they don't offer the i5 2500K I doubt they will provide it it but you can ask. The whole K designation is for i5 chips that can be overclocked which you aren't going to be doing so a standard i5 2500 should be just fine and it is cheaper -- if they offer it.

Seriously, your original system configuration is quite fine for gaming and the 6770 will be okay. My suggestion is go ahead and ask them if they do offer the option of a 6850 or 6950 OR a GTX 460 or GTX 560 Ti. It doesn't hurt to ask. If not then save up and buy another card and keep or sell your 6770.